Gas separation is useful in many industries and can typically be accomplished by flowing a mixture of gases over an adsorbent material that preferentially adsorbs one or more gas components while not adsorbing one or more other gas components. The non-adsorbed components are recovered as a separate product.
One particular type of gas separation technology is swing adsorption, such as temperature swing adsorption (TSA), pressure swing adsorption (PSA), partial pressure swing adsorption (PPSA), rapid cycle pressure swing adsorption (RCPSA), rapid cycle partial pressure swing adsorption (RCPPSA), and not limited to but also combinations of the fore mentioned processes, such as pressure and temperature swing adsorption. As an example, PSA processes rely on the phenomenon of gases being more readily adsorbed within the pore structure or free volume of an adsorbent material when the gas is under pressure. That is, the higher the gas pressure, the greater the amount of readily-adsorbed gas adsorbed. When the pressure is reduced, the adsorbed component is released, or desorbed from the adsorbent material.
PSA processes may be used to separate gases of a gas mixture because different gases tend to fill the micropore of the adsorbent material to different extents. If a gas mixture, such as natural gas, is passed under pressure through a vessel containing an adsorbent material that is more selective towards carbon dioxide than it is for methane, at least a portion of the carbon dioxide is selectively adsorbed by the adsorbent material, and the gas exiting the vessel is enriched in methane. When the adsorbent material reaches the end of its capacity to adsorb carbon dioxide, it is regenerated by reducing the pressure, thereby releasing the adsorbed carbon dioxide. The adsorbent material is then typically purged and repressurized. Then, the adsorbent material is ready for another adsorption cycle.
TSA processes rely on the phenomenon that gases at lower temperatures are more readily adsorbed within the pore structure or free volume of an adsorbent material compared to higher temperatures. That is, when the temperature of the adsorbent material is increased, the adsorbed gas is released, or desorbed. By cyclically swinging the temperature of an adsorbent material (e.g., an adsorbent bed), TSA processes can be used to separate gases in a mixture when used with an adsorbent material that is selective for one or more of the components of a gas mixture.
In these swing adsorption processes, various adsorbent bed assemblies may be coupled together with conduits and valves to manage the flow of fluids. Orchestrating these adsorbent bed assemblies involves coordinating the cycles for each of the adsorbent bed assemblies with other adsorbent bed assemblies in the system. A complete cycle can vary from seconds to minutes as it transfers a plurality of gaseous streams through one or more of the adsorbent bed assemblies.
Despite the benefits of the swing adsorption processes, swing adsorption systems do not properly manage the fluid flow within the system. For example, typically, the gas from the previous stream has to be displaced as part of the process. As these streams may be at different pressures, the result is pulsation in the feed and product flows. Even the grouping of different adsorbent bed assemblies together with a shared manifold fails to adequately address this problem. For example, RCPSA involves rapid acting valves capable of tight sealing, and reduced dead volume. A process that involves large pressure swings (e.g., 85 to 1.2 BARA) and short cycle time (e.g., less than 60 second, less than 20 seconds, or less than 10 seconds) may have pulsation in the headers. For some flow service duties, the pulsation can interfere with the flow rate through the adsorbent bed, from end to end (where a valve is open on both ends at once) or in adjacent vessels (e.g., where the valve opening times overlap.). The pulsation can cause unwanted mechanical vibrations, which may shorten the life of various components within the system.
Accordingly, there remains a need in the industry for apparatus, methods, and systems that are more efficient and can be constructed to lessen the pulsation of fluid flow through the system. The more efficient management of the streams is beneficial when the swing adsorption processes involve the rapid cycles. Further, there is a need for an enhanced method and apparatus to implement an industrial-scale, adsorbent bed unit, which has valves that enhance the cycle time and manage the steady flow of fluids between cycles. The present techniques provide a method and apparatus that overcome one or more of the deficiencies discussed above.